What Is a Digital Camera Viewfinder?

You may have heard it called a diopter, but really, it's not

You may have heard a camera viewfinder called a diopter, but really, it's not. A digital camera viewfinder is a viewing mechanism on the back of a DSLR (digital single lens reflex) camera that allows the photographer to see the image that will be captured. But there is also much more to a camera viewfinder. There are different types, and different mechanisms. Here's what you should know about the various viewfinders.

Someone using a DSLR camera with the digital LCD screen on display.
 @FreshMaks via Twenty20

What Is a Viewfinder?

A digital camera viewfinder is the part of the camera that is used to frame and setup a photograph. It is usually located on the back of the camera, and can be either an optical viewfinder or a digital, or electronic viewfinder (EVF).

  • Optical Viewfinder: An optical viewfinder is most often found on DSLR cameras. You'll know it as the eye piece on the back of the camera, usually toward the top. This is a viewing mechanism that uses a method of reflection to show the photographer a view of the scene through the lens of the camera. Optical viewfinders may also show some digital information in the viewing field about the the camera settings or shooting information about the scene the lens is focused on. And optical viewfiders work well in both bright and low light conditions.
  • Digital Viewfinder: These may also be called electronic viewfinders (EVFs) because a digital viewfinder shows an enhanced digital image of the image traveling through the camera lens. This means the image you see through a digital viewfinder may not be exactly the view that the lens is capturing. Digital viewfinders do have some advantages, though. For example, a digital viewfinder may show a more accurate representation of the lighting conditions for the scene that is in focus.

There's also another type of viewfinder, though it is often lumped into the digital viewfinder category: the viewfinder screen. This is the screen on the back of most DSLR cameras where photographers can change settings, scroll through captured images, and in some cases, make some minor changes or corrections to the image. This screen, which is usually about two to two and a half inches square, can also be used to frame a scene and focus the camera.

And, in some cases, the viewfinder screen is a better option than the optical or digital viewfinder located on the body of the camera. For example, if you're shooting in a place where it's awkward to hold the camera to your face, the viewfinder screen may help you focus better, especially if it's an articulating screen that can move left and right as well as up and down.

How a Viewfinder Works

How a viewfinder works is determined by the type of viewfinder you're using. An optical viewfinder uses either a pentaprism or a pentamirror to reflect the image traveling through the camera lens up to the viewfinder. If the optical viewfinder uses a pentaprism, then the image is reflected through the prism. This is often how high-end DSLR camera viewfinders work.

Lower-end and entry-level DSLR cameras typically use the pentamirror viewfinder system, where the image traveling through the lens is reflected into the viewfinder using a series of mirrors. These mirrors are often plastic, and can be heard moving when the camera shutter button is pressed. That's because pentamirror systems have a mirror located directly in front of the image sensor, and it has to flip up and out of the way for the image to be captured.

Both types of optical viewfinders work very well for capturing accurate images as long as the diopter, which is the lens in front of viewfinder, is adjusted properly for the photographer's vision.

Electronic viewfinders work in a similar fashion, except the image that is reflected into the viewfinder is not the image that travels through the camera lens. Instead, it is a digital representation of that image.

The downfall of electronic viewfinders is that they consume battery power, which shortens the amount of time that you can shoot, and if the resolution of the digital viewfinder doesn't match the resolution of the camera, you might not be seeing an accurate image of the scene you are trying to photograph.

As mirrorless cameras become more popular, digital viewfinders are becoming more commonplace because mirrorless cameras do not have optical viewfinders.

Which is Better, an Optical or a Digital Viewfinder?

It's common for a new photographer to wonder whether an optical or digital viewfinder is best to use. The problem is, each is better in certain situations.

For example, an optical viewfinder is always better in very bright situations, because it helps reduce the amount of glare your eye sees so you can see the image that's traveling through your lens better.

However, if you're shooting in lower light conditions, the digital viewfinder might do a better job of accurately representing the amount of light that's traveling through your lens.

In general, most professional photographers prefer the optical viewfinder because it provides the most accurate representation of the image that is traveling through the lens in most situations. The optical viewfinder also provides a way to brace the camera while you're shooting, since it need to be brought to your face to so you can look through the viewfinder. This, combined with keeping your elbows close to your body, can help stabilize the camera and reduce the amount of shake that can occur if you're trying to hold the camera away from your body.